Force detector and robot

ABSTRACT

A force detector includes a first base, a second base, and a sensor therebetween. The sensor includes a side wall having a terminal, a sensor plate connected to one end of the side wall, a lid connected to the other end of the side wall to configure an inner space, a charge output element in the inner space, and a conductor electrically connecting the charge output element to the terminal. The sensor plate is between the first base and the charge output element. The lid is between the second base and the charge output element. An elastic modulus of the sensor plate is lower than that of the side wall. The charge output element includes crystal. The sensor plate includes a metal selected from stainless steel, Kovar, copper, iron, carbon steel, and titanium.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation patent application of U.S. application Ser. No.15/284,842, filed on Oct. 4, 2016, which is a continuation of U.S.application Ser. No. 14/624,882, filed on Feb. 18, 2015, now U.S. Pat.No. 9,481,089, issued on Nov. 1, 2016, which claims priority to JapanesePatent Application No. 2014-036417, filed on Feb. 27, 2014. All theabove applications are expressly incorporated by reference herein intheir entireties.

BACKGROUND 1. Technical Field

The present invention relates to a force detector and a robot.

2. Related Art

Recently, introduction of industrial robots to production facilitiesincluding factories has been promoted for improvement in productionefficiency. As the industrial robots, machine tools for machining parentmaterials such aluminum boards are representative. Some machine toolsinclude force detectors that detect forces on the parent materials atmachining (for example, see Patent Document 1 (JP-2013-130431)).

Patent Document 1 discloses a sensor device including a piezoelectricelement, a ceramic package having a recessed part for housing thepiezoelectric element, and a lid joined to the ceramic package to closethe opening of the recessed part with the piezoelectric element housedwithin the recessed part of the ceramic package. Further, the sensordevice is sandwiched by two pressurization plates.

In the sensor device, when an external force is applied to thepressurization plate, the external force is transmitted to thepiezoelectric element via the ceramic package and the lid, thepiezoelectric element outputs electric charge in response to theexternal force, and thereby, the applied external force may be detectedbased on the electric charge.

Further, the sensor device is air-tightly sealed by the ceramic packageand the lid and shielded from outside air. Thereby, the electric chargegenerated from the piezoelectric element is prevented from unintendedlyleaking to the outside due to moisture or the like.

However, in the force detector disclosed in Patent Document 1, there isa problem that external forces are repeatedly applied to thepressurization plates, and thereby, stress is repeatedly applied to theceramic package and the ceramic package is broken. Accordingly, it isdifficult to use the force detector stably over a long period.

Further, in the force detector, there is another problem that, atmanufacturing, when the sensor device is sandwiched by thepressurization plates, the ceramic package is broken due to the pressureapplied by the pressurization plates.

SUMMARY

Accordingly, an advantage of some aspects of the invention is to providea force detector that may reduce breakage of a housing part (package)housing a piezoelectric element even when external forces are repeatedlyapplied, and a robot.

The advantage is achieved by the following aspects or applicationexamples of the invention.

Application Example 1

A force detector according to this application example of the inventionincludes a first base part, a second base part, and a pressure detectionunit provided between the first base part and the second base part andincluding a piezoelectric element that outputs a signal in response toan external force, wherein the pressure detection unit has a firstmember having a portion in contact with the first base part, a secondmember having a portion in contact with the second base part, and athird member connecting the first member and the second member, a firstlongitudinal elastic modulus of at least a part of the first member islower than a third longitudinal elastic modulus of the third member, anda second longitudinal elastic modulus of at least a part of the secondmember is lower than the third longitudinal elastic modulus of the thirdmember.

With this configuration, even when external forces are repeatedlyapplied to the first base part and the second base part, the firstmember and the second member may be deformed in response to the externalforces. Accordingly, even when external forces are repeatedly applied,breakage of a housing part housing the piezoelectric element may bereduced.

Application Example 2

In the force detector according to this application example of theinvention, it is preferable that a difference between the firstlongitudinal elastic modulus and the second longitudinal elastic modulusis a tenth part or less of the first longitudinal elastic modulus.

With this configuration, concentration of stress on only one of thefirst member and the second member may be avoided, and therefore,breakage of the housing part housing the piezoelectric element may bereduced more reliably.

Application Example 3

In the force detector according to this application example of theinvention, it is preferable that a constituent material of the firstmember and a constituent material of the second member are the same.

With this configuration, concentration of the applied external force ononly one of the first member and the second member may be avoided, andtherefore, unintended deformation and breakage of the housing parthousing the piezoelectric element may be reduced particularlyeffectively.

Application Example 4

In the force detector according to this application example of theinvention, it is preferable that a constituent material of the thirdmember contains ceramic.

With this configuration, the mechanical strength as the whole housingpart may be sufficiently secured. Therefore, even when external forcesare repeatedly applied thereto, damage by the deformation of the housingpart is harder to be caused, and the piezoelectric element housed insidemay be protected more reliably.

Application Example 5

In the force detector according to this application example of theinvention, it is preferable that the longitudinal elastic modulus of thefirst member is the first longitudinal elastic modulus.

With this configuration, the first member may be formed by a singlemember and a single material, and the longitudinal elastic modulus(Young modulus) and the mechanical strength may be homogenized over thewhole first member. Accordingly, breakage of the first member due to theapplied external force may be reduced more reliably, and the externalforce may be transmitted to the piezoelectric element via the firstmember more accurately.

Application Example 6

In the force detector according to this application example of theinvention, it is preferable that the longitudinal elastic modulus of thesecond member is the second longitudinal elastic modulus.

With this configuration, the second member may be formed by a singlemember and a single material, and the longitudinal elastic modulus(Young modulus) and the mechanical strength may be homogenized over thewhole second member. Accordingly, breakage of the second member due tothe applied external force may be reduced more reliably, and theexternal force may be transmitted to the piezoelectric element via thesecond member more accurately.

Application Example 7

In the force detector according to this application example of theinvention, it is preferable that the piezoelectric element containscrystal.

With this configuration, the force detector is harder to be influencedby temperature variations, and therefore, may accurately detect theexternal force.

Application Example 8

In the force detector according to this application example of theinvention, it is preferable that the piezoelectric element is locatedinside of the pressure detection unit.

With this configuration, the piezoelectric element is sealed andshielded from outside air, and therefore, output electric charge isprevented from unintendedly leaking due to moisture or the like.

Application Example 9

A robot according to this application example of the invention includesan arm, an end effector provided on the arm, and a force detectorprovided between the arm and the end effector and detecting an externalforce applied to the end effector, the force detector includes a firstbase part, a second base part, and a pressure detection unit providedbetween the first base part and the second base part and including apiezoelectric element that outputs a signal in response to an externalforce, wherein the pressure detection unit has a first member having aportion in contact with the first base part, a second member having aportion in contact with the second base part, and a third memberconnecting the first member and the second member, a first longitudinalelastic modulus of at least a part of the first member is lower than athird longitudinal elastic modulus of the third member, and a secondlongitudinal elastic modulus of at least a part of the second member islower than the third longitudinal elastic modulus of the third member.

With this configuration, in the robot, even when external forces arerepeatedly applied to the pressure detection unit, breakage of thehousing part housing the piezoelectric element may be reduced.Therefore, according to the robot, the external forces may be accuratelydetected and work by the end effector may be properly performed.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a sectional view showing a force detector according to a firstembodiment of the invention.

FIG. 2 is a plan view of the force detector shown in FIG. 1.

FIG. 3 is a circuit diagram schematically showing the force detectorshown in FIG. 1.

FIG. 4 is a sectional view schematically showing a charge output elementprovided in the force detector shown in FIG. 1.

FIG. 5 is a schematic diagram showing an acting state of a forcedetected by the charge output element of the force detector shown inFIG. 1.

FIG. 6 is a diagram as seen from an arrow D in FIG. 5.

FIG. 7 is a partially enlarged detail view around the charge outputelement of the force detector shown in FIG. 1.

FIG. 8 shows an example of a single-arm robot using the force detectoraccording to the embodiment of the invention.

FIG. 9 shows an example of a multi-arm robot using the force detectoraccording to the embodiment of the invention.

FIG. 10 shows an example of an electronic part inspection apparatus anda part carrying apparatus using the force detector according to theembodiment of the invention.

FIG. 11 shows an example of an electronic part carrying apparatus usingthe force detector according to the embodiment of the invention.

FIG. 12 shows an example of a part machining apparatus using the forcedetector according to the embodiment of the invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

As below, preferred embodiments of the invention will be explained indetail.

1. Force Detector

FIG. 1 is a sectional view showing a force detector according to a firstembodiment of the invention, FIG. 2 is a plan view of the force detectorshown in FIG. 1, FIG. 3 is a circuit diagram schematically showing theforce detector shown in FIG. 1, FIG. 4 is a sectional view schematicallyshowing a charge output element provided in the force detector shown inFIG. 1, FIG. 5 is a schematic diagram showing an acting state of a forcedetected by the charge output element of the force detector shown inFIG. 1, FIG. 6 is a diagram as seen from an arrow D in FIG. 5, and FIG.7 is a partially enlarged detail view around the charge output elementof the force detector shown in FIG. 1.

Note that, as below, the upside in FIG. 1 is referred to as “upper” or“above” and the downside is referred to as “lower” or “below”.

In FIGS. 2 and 5, as three axes orthogonal to one another, an α-axis, aβ-axis, and a γ-axis are shown. Further, in FIGS. 1 and 4, of the threeaxes, only the γ-axis is shown. A direction in parallel to the α(A)-axisis referred to as “α(A)-axis direction”, a direction in parallel to theβ(B)-axis is referred to as “β(B)-axis direction”, and a direction inparallel to the γ(C)-axis is referred to as “γ(C)-axis direction”. Aplane defined by the α-axis and the β-axis is referred to as “αβ-plane”,a plane defined by the β-axis and the γ-axis is referred to as“βγ-plane”, and a plane defined by the α-axis and the γ-axis is referredto as “αγ-plane”. A direction in parallel to the α-axis is referred toas “α direction”, a direction in parallel to the β-axis is referred toas “β-direction”, and a direction in parallel to the γ-axis is referredto as “γ direction”. Further, in the α direction, the β direction, andthe γ direction, the pointing end side of an arrow is referred to as“+(positive) side” and the base end side of the arrow is referred to as“−(negative) side”.

A force detector 1 shown in FIG. 1 has a function of detecting externalforces applied to the force detector 1, i.e., six-axis forces(translational force components in the α-, β-, and γ-axis directions androtational force components around the α-, β-, and γ-axes).

The force detector 1 includes a first base part (base part) 2, a secondbase part (base part) 3 provided at a predetermined distance from thefirst base part 2 and opposed to the first base part 2, analog circuitboards 4 housed (provided) between the first base part 2 and the secondbase part 3, a digital circuit board 5 housed (provided) between thefirst base part 2 and the second base part 3 and electrically connectedto the analog circuit boards 4, four sensor devices (pressure detectionunits) 6 mounted on the analog circuit boards 4 and having charge outputelements (piezoelectric elements) 10 that output signals in response toexternal forces and packages (housing parts) 60 that house the chargeoutput elements 10, and eight pressurization bolts (fixing members) 71.

As below, configurations of the respective parts of the force detector 1will be described in detail.

Note that, in the following explanation, as shown in FIG. 2, of the foursensor devices 6, the sensor device 6 located on the right side in FIG.2 is referred to as “sensor device 6A”, and, sequentially in thecounter-clockwise direction, the sensor devices are referred to as“sensor device 6B”, “sensor device 6C”, and “sensor device 6D”.

As shown in FIG. 1, the first base part (base plate) 2 has a plate-likeouter shape, and a rounded rectangular planar shape. The planar shape ofthe first base part 2 is not limited to the shown shape, but may be acircular shape or another polygonal shape than the rectangular shape,for example.

A lower surface 221 of the first base part 2 functions, when the forcedetector 1 is fixed to, e.g., a robot and used, as a mounting surface(first mounting surface) for the robot (measuring object).

The first base part 2 has a bottom plate 22 and wall parts 24 stoodupward from the bottom plate 22.

The wall parts 24 have “L” shapes and convex portions 23 respectivelyformed on two surfaces facing outward to project. The top surfaces(first surfaces) 231 of the respective convex portions are flat surfacesperpendicular to the bottom plate 22. Further, in the convex portions23, internal threads 241 screwed with the pressurization bolts 71, whichwill be described later, are provided (see FIG. 2).

As shown in FIG. 1, the second base part (cover plate) 3 is provided tobe opposed to the first base part 2 at a predetermined distance.

The second base part 3 also has a plate-like outer shape like the firstbase part 2. Further, it is preferable that the planar shape of thesecond base part 3 is a shape corresponding to the planar shape of thefirst base part 2, and, in the embodiment, the plan view shape of thesecond base part 3 is a rectangular shape with rounded corners like theplan view shape of the first base part 2. Furthermore, it is preferablethat the second base part 3 has a size containing the first base part 2.

An upper surface (second surface) 321 of the second base part 3functions, when the force detector 1 is fixed to, e.g., a robot andused, as a mounting surface (second mounting surface) for an endeffector (measuring object) attached to the robot. Further, the uppersurface 321 of the second base part 3 and the above described lowersurface 221 of the first base part 2 are in parallel under naturalconditions without application of external forces.

The second base part 3 has a top plate 32 and side walls 33 formed on anedge part of the top plate 32 and projecting downward from the edgepart. Inner wall surfaces (second surfaces) 331 of the side walls 33 areflat surfaces perpendicular to the top plate 32. Further, the sensordevices 6 are provided between the top surfaces 231 of the first basepart 2 and the inner wall surfaces 331 of the second base part 3.

The first base part 2 and the second base part 3 are connected andfastened by the pressurization bolts 71. As shown in FIG. 2, there areeight (a plurality of) pressurization bolts 71 and two of them each areprovided on both sides of the respective sensor devices 6. Note that thenumber of pressurization bolts 71 for each sensor device 6 is notlimited to two, but may be three or more, for example.

Further, the constituent material of the pressurization bolts 71 is notparticularly limited. For example, various resin materials, variousmetal materials, etc. may be used.

The first base part 2 and the second base part 3 connected by thepressurization bolts 71 form a housing space for housing the sensordevices 6A to 6D, the analog circuit boards 4, and the digital circuitboard 5. The housing space has a sectional shape of circle or squarewith rounded corners.

As shown in FIG. 1, the analog circuit boards 4 connected to the sensordevices 6 are provided between the first base part 2 and the second basepart 3.

In the parts of the analog circuit boards 4 in which the sensor devices6 (specifically, the charge output elements 10) are provided, holes 41for insertion of the respective convex portions 23 of the first basepart 2 are formed. The holes 41 are through holes penetrating the analogcircuit boards 4.

Further, as shown in FIG. 2, through holes penetrated by the respectivepressurization bolts 71 are provided in the analog circuit boards 4, andpipes 43 formed using an insulating material of a resin material or thelike are fixed to the parts penetrated by the respective pressurizationbolts 71 of the analog circuit boards 4 (through holes) by fitting, forexample.

Furthermore, as shown in FIG. 3, the analog circuit board 4 connected tothe sensor device 6A includes a conversion output circuit 90 a thatconverts electric charge Qy1 output from the charge output element 10 ofthe sensor device 6A into a voltage Vy1, a conversion output circuit 90b that converts electric charge Qz1 output from the charge outputelement 10 into a voltage Vz1, and a conversion output circuit 90 c thatconverts electric charge Qx1 output from the charge output element 10into a voltage Vx1.

The analog circuit board 4 connected to the sensor device 6B includes aconversion output circuit 90 a that converts electric charge Qy2 outputfrom the charge output element 10 of the sensor device 6B into a voltageVy2, a conversion output circuit 90 b that converts electric charge Qz2output from the charge output element 10 into a voltage Vz2, and aconversion output circuit 90 c that converts electric charge Qx2 outputfrom the charge output element 10 into a voltage Vx2.

The analog circuit board 4 connected to the sensor device 6C includes aconversion output circuit 90 a that converts electric charge Qy3 outputfrom the charge output element 10 of the sensor device 6C into a voltageVy3, a conversion output circuit 90 b that converts electric charge Qz3output from the charge output element 10 into a voltage Vz3, and aconversion output circuit 90 c that converts electric charge Qx3 outputfrom the charge output element 10 into a voltage Vx3.

The analog circuit board 4 connected to the sensor device 6D includes aconversion output circuit 90 a that converts electric charge Qy4 outputfrom the charge output element 10 of the sensor device 6D into a voltageVy4, a conversion output circuit 90 b that converts electric charge Qz4output from the charge output element 10 into a voltage Vz4, and aconversion output circuit 90 c that converts electric charge Qx4 outputfrom the charge output element 10 into a voltage Vx4.

As shown in FIG. 1, the digital circuit board 5 connected to andsupported by the analog circuit boards 4 is provided between the firstbase part 2 and the second base part 3 in a position different from thepositions in which the analog circuit boards 4 are provided on the firstbase part 2. As shown in FIG. 3, the digital circuit board 5 includes anexternal force detection circuit 40 having an AD converter 401 connectedto the conversion output circuits (conversion circuits) 90 a, 90 b, 90 cand a calculation part (calculation circuit) 402 connected to the ADconverter 401.

Note that the constituent materials of the first base part 2, the secondbase part 3, the other parts than the respective elements and therespective wires of the analog circuit boards 4, and the other partsthan the respective elements and the respective wires of the digitalcircuit board 5 are not particularly limited. For example, various resinmaterials, various metal materials, etc. may be used.

Further, the first base part 2 and the second base part 3 arerespectively formed by the members having the plate-like outer shapes,however, not limited to those. For example, one base part may be formedby a plate-like member and the other base part may be formed by ablock-like member.

Next, the sensor devices 6 will be explained in detail.

Sensor Devices

As shown in FIGS. 1 and 2, the sensor device 6A is sandwiched by the topsurface 231 of one convex portion 23 of the four convex portions 23 ofthe first base part 2 and the inner wall 331 opposed to the top surface231. Like the sensor device 6A, the sensor device 6B is sandwiched bythe top surface 231 of one convex portion 23 different from the portionand the inner wall 331 opposed to the top surface 231. Further, thesensor device 6C is sandwiched by the top surface 231 of one convexportion 23 different from the portion and the inner wall 331 opposed tothe top surface 231. Furthermore, the sensor device 6D is sandwiched bythe top surface 231 of one convex portion 23 different from the portionand the inner wall 331 opposed to the top surface 231.

Note that, as below, the directions in which the respective sensordevices 6A to 6D are sandwiched by the first base part 2 and the secondbase part 3 are referred to as “sandwich directions SD”. Further, thedirection in which the first sensor device 6A of the respective sensordevices 6A to 6D is sandwiched may be referred to as “first sandwichdirection”, the direction in which the second sensor device 6B issandwiched may be referred to as “second sandwich direction”, thedirection in which the third sensor device 6C is sandwiched may bereferred to as “third sandwich direction”, and the direction in whichthe fourth sensor device 6D is sandwiched may be referred to as “fourthsandwich direction”.

Note that, in the embodiment, as shown in FIG. 1, the sensor devices 6are provided at the second base part 3 (side walls 33) side of theanalog circuit boards 4, however, the sensor devices 6 may be providedat the first base part 2 side of the analog circuit boards 4.

Further, as shown in FIG. 2, the sensor device 6A and the sensor device6B, the sensor device 6C and the sensor device 6D are symmetricallyprovided with respect to a center axis 271 along the β-axis of the firstbase part 2. That is, the sensor devices 6A to 6D are provided at equalangular intervals around a center 272 of the first base part 2. Thesensor devices 6A to 6D are provided as described above, and thereby,external forces may be detected without deviation.

The arrangement of the sensor devices 6A to 6D is not limited to theillustrated one. It is preferable that the sensor devices 6A to 6D areprovided in positions as far apart as possible from the center part(center 272) of the second base part 3 as seen from the upper surface321 of the second base part 3. Thereby, external forces applied to theforce detector 1 may be stably detected.

Further, in the embodiment, all of the sensor devices 6A to 6D aremounted in the same orientation, however, the orientations of the sensordevices 6A to 6D may be different from one another.

Thus arranged sensor devices 6 have the charge output elements 10 andpackages 60 housing the charge output elements 10 as shown in FIG. 1.Further, in the embodiment, the sensor devices 6A to 6D have the sameconfiguration.

As below, the charge output elements 10 of the sensor devices 6 will bedescribed in detail. Note that the packages housing the charge outputelements 10 will be described later in detail.

Charge Output Elements

The charge output element 10 has a function of outputting electriccharge in response to an external force applied to the force detector 1,i.e., an external force applied to one base part of the first base part2 and the second base part 3.

The respective charge output elements 10 of the sensor devices 6A to 6Dhave the same configuration, and one charge output element 10 will becentered for explanation.

As shown in FIG. 4, the charge output element 10 of the sensor device 6has ground electrode layers 11, a first sensor 12, a second sensor 13,and a third sensor 14.

The first sensor 12 has a function of outputting electric charge Qx (oneof electric charge Qx1, Qx2, Qx3, Qx4) in response to an external force(shear force). The second sensor 13 has a function of outputtingelectric charge Qz (Qz1, Qz2, Qz3, Qz4) in response to an external force(compression/tension force). The third sensor 14 has a function ofoutputting electric charge Qy (Qy1, Qy2, Qy3, Qy4) in response to anexternal force (shear force).

In the charge output element 10 of the sensor device 6, the groundelectrode layers 11 and the respective sensors 11, 12, 13 arealternately laminated in parallel. As below, the lamination direction isreferred to as “lamination direction LD”. The lamination direction LD isorthogonal to a normal NL₂ of the upper surface 321 (or a normal NL₁ ofthe lower surface 221). Further, the lamination direction LD is inparallel to the sandwich direction SD.

The shape of the charge output element 10 is not particularly limited,however, in the embodiment, a rectangular shape as seen from a directionperpendicular to the inner wall surface 331 of each side surface 33. Theother outer shapes of the respective charge output elements 10 include,e.g., other polygonal shapes of pentagonal shapes, circular shapes, ovalshapes, etc.

As below, the ground electrode layers 11, the first sensor 12, thesecond sensor 13, and the third sensor 14 will be described in detail.

The ground electrode layer 11 is an electrode grounded to the ground(reference potential point). The material constituting the groundelectrode layer 11 is not particularly limited. For example, gold,titanium, aluminum, copper, iron, or an alloy containing the metals ispreferably used. Of them, particularly, stainless as an iron alloy ispreferably used. The ground electrode layer 11 including the stainlesshas advantageous durability and corrosion resistance.

The first sensor 12 has a function of outputting electric charge Qx inresponse to an external force (shear force) in the first detectiondirection orthogonal to the lamination direction LD (first sandwichdirection), i.e., the same direction as the direction of the normal NL₂(normal NL₁). That is, the first sensor 12 is adapted to output positivecharge or negative charge in response to an external force.

The first sensor 12 has a first piezoelectric layer (first detectionplate) 121, a second piezoelectric layer (first detection plate) 123provided to be opposed to the first piezoelectric layer 121, and anoutput electrode layer 122 provided between the first piezoelectriclayer 121 and the second piezoelectric layer 123.

The first piezoelectric layer 121 is formed by a Y-cut crystal plate andhas an x-axis, a y-axis, and a z-axis orthogonal to one another. They-axis is an axis along the thickness direction of the firstpiezoelectric layer 121, the x-axis is an axis along the paper depthdirection in FIG. 4, and the z-axis is an axis along the longitudinaldirection in FIG. 4.

As below, the explanation will be made with the pointing end sides ofthe respective arrows as “+(positive)” and the base end sides of thearrows as “−(negative)”. Further, the direction in parallel to thex-axis is referred to as “x-axis direction”, the direction in parallelto the y-axis is referred to as “y-axis direction”, and the direction inparallel to the z-axis is referred to as “z-axis direction”. Note thatthis applies to the second piezoelectric layer 123, a thirdpiezoelectric layer 131, a fourth piezoelectric layer 133, a fifthpiezoelectric layer 141, and a sixth piezoelectric layer 143, which willbe described later.

The first piezoelectric layer 121 including crystal has advantageousproperties such as a wider dynamic range, higher rigidity, a highernatural frequency, and higher load bearing. Further, the Y-cut crystalplate generates electric charge for the external force (shear force)along the surface direction thereof.

When an external (shear) force along the positive direction of thex-axis is applied to the surface of the first piezoelectric layer 121,electric charge is induced within the first piezoelectric layer 121 dueto the piezoelectric effect. As a result, positive charge collects nearthe surface at the output electrode layer 122 side of the firstpiezoelectric layer 121, and negative charge collects near the surfaceat the ground electrode layer 11 side of the first piezoelectric layer121. Similarly, when an external force along the negative direction ofthe x-axis is applied to the surface of the first piezoelectric layer121, negative charge collects near the surface at the output electrodelayer 122 side of the first piezoelectric layer 121, and positive chargecollects near the surface at the ground electrode layer 11 side of thefirst piezoelectric layer 121.

The second piezoelectric layer 123 is also formed by a Y-cut crystalplate and has an x-axis, a y-axis, and a z-axis orthogonal to oneanother. The y-axis is an axis along the thickness direction of thesecond piezoelectric layer 123, the x-axis is an axis along the paperdepth direction in FIG. 4, and the z-axis is an axis along thelongitudinal direction in FIG. 4.

Like the first piezoelectric layer 121, the second piezoelectric layer123 including crystal has advantageous properties such as a widerdynamic range, higher rigidity, a higher natural frequency, and higherload bearing, and the Y-cut crystal plate generates electric charge forthe external force (shear force) along the surface direction thereof.

When an external force (shear force) along the positive direction of thex-axis is applied to the surface of the second piezoelectric layer 123,electric charge is induced within the second piezoelectric layer 123 dueto the piezoelectric effect. As a result, positive charge collects nearthe surface at the output electrode layer 122 side of the secondpiezoelectric layer 123, and negative charge collects near the surfaceat the ground electrode layer 11 side of the second piezoelectric layer123. Similarly, when an external force along the negative direction ofthe x-axis is applied to the surface of the second piezoelectric layer123, negative charge collects near the surface at the output electrodelayer 122 side of the second piezoelectric layer 123, and positivecharge collects near the surface at the ground electrode layer 11 sideof the second piezoelectric layer 123.

The output electrode layer 122 has a function of outputting positivecharge or negative charge generated within the first piezoelectric layer121 and the second piezoelectric layer 123 as electric charge Qx. Asdescribed above, when an external force along the positive direction ofthe x-axis is applied to the surface of the first piezoelectric layer121 or the surface of the second piezoelectric layer 123, positivecharge collects near the output electrode layer 122. As a result,positive charge Qx is output from the output electrode layer 122. On theother hand, when an external force along the negative direction of thex-axis is applied to the surface of the first piezoelectric layer 121 orthe surface of the second piezoelectric layer 123, negative chargecollects near the output electrode layer 122. As a result, negativecharge Qx is output from the output electrode layer 122.

Further, the configuration of the first sensor 12 having the firstpiezoelectric layer 121 and the second piezoelectric layer 123 mayincrease the positive charge or negative charge collecting near theoutput electrode layer 122 compared to the configuration having only oneof the first piezoelectric layer 121 and the second piezoelectric layer123 and the output electrode layer 122. As a result, the electric chargeQx output from the output electrode layer 122 may be increased. Thisapplies to the second sensor 13 and the third sensor 14, which will bedescribed later.

It is preferable that the size of the output electrode layer 122 isequal to or larger than the sizes of the first piezoelectric layer 121and the second piezoelectric layer 123. When the output electrode layer122 is smaller than the first piezoelectric layer 121 or the secondpiezoelectric layer 123, part of the first piezoelectric layer 121 orthe second piezoelectric layer 123 is not in contact with the outputelectrode layer 122. Accordingly, it may be impossible to output part ofthe electric charge generated in the first piezoelectric layer 121 orthe second piezoelectric layer 123 from the output electrode layer 122.As a result, the electric charge Qx output from the output electrodelayer 122 decreases. This applies to output electrode layers 132, 142,which will be described later.

The second sensor 13 has a function of outputting electric charge Qz inresponse to an external force (compression/tension force). That is, thesecond sensor 13 is adapted to output positive charge in response to acompression force and negative charge in response to a tension force.

The second sensor 13 has the third piezoelectric layer (third substrate)131, the fourth piezoelectric layer (third substrate) 133 provided to beopposed to the third piezoelectric layer 131, and the output electrodelayer 132 provided between the third piezoelectric layer 131 and thefourth piezoelectric layer 133.

The third piezoelectric layer 131 is formed by an X-cut crystal plateand has an x-axis, a y-axis, and a z-axis orthogonal to one another. Thex-axis is an axis along the thickness direction of the thirdpiezoelectric layer 131, the y-axis is an axis along the longitudinaldirection in FIG. 4, and the z-axis is an axis along the paper depthdirection in FIG. 4.

When a compression force in parallel to the x-axis is applied to thesurface of the third piezoelectric layer 131, electric charge is inducedwithin the third piezoelectric layer 131 due to the piezoelectriceffect. As a result, positive charge collects near the surface at theoutput electrode layer 132 side of the third piezoelectric layer 131,and negative charge collects near the surface at the ground electrodelayer 11 side of the third piezoelectric layer 131. Similarly, when atension force in parallel to the x-axis is applied to the surface of thethird piezoelectric layer 131, negative charge collects near the surfaceat the output electrode layer 132 side of the third piezoelectric layer131, and positive charge collects near the surface at the groundelectrode layer 11 side of the third piezoelectric layer 131.

The fourth piezoelectric layer 133 is also formed by an X-cut crystalplate and has an x-axis, a y-axis, and a z-axis orthogonal to oneanother. The x-axis is an axis along the thickness direction of thefourth piezoelectric layer 133, the y-axis is an axis along thelongitudinal direction in FIG. 4, and the z-axis is an axis along thepaper depth direction in FIG. 4.

When a compression force in parallel to the x-axis is applied to thesurface of the fourth piezoelectric layer 133, electric charge isinduced within the fourth piezoelectric layer 133 due to thepiezoelectric effect. As a result, positive charge collects near thesurface at the output electrode layer 132 side of the fourthpiezoelectric layer 133, and negative charge collects near the surfaceat the ground electrode layer 11 side of the fourth piezoelectric layer133. Similarly, when a tension force in parallel to the x-axis isapplied to the surface of the fourth piezoelectric layer 133, negativecharge collects near the surface at the output electrode layer 132 sideof the fourth piezoelectric layer 133, and positive charge collects nearthe surface at the ground electrode layer 11 side of the fourthpiezoelectric layer 133.

The output electrode layer 132 has a function of outputting electricpositive charge or negative charge generated within the thirdpiezoelectric layer 131 and the fourth piezoelectric layer 133 aselectric charge Qz. As described above, when a compression force inparallel to the x-axis is applied to the surface of the thirdpiezoelectric layer 131 or the surface of the fourth piezoelectric layer133, positive charge collects near the output electrode layer 132. As aresult, positive charge Qz is output from the output electrode layer132. On the other hand, when a tension force in parallel to the x-axisis applied to the surface of the third piezoelectric layer 131 or thesurface of the fourth piezoelectric layer 133, negative charge collectsnear the output electrode layer 132. As a result, negative charge Qz isoutput from the output electrode layer 132.

The third sensor 14 has a function of outputting electric charge Qx inresponse to an external force (shear force) in the second detectiondirection orthogonal to the lamination direction LD (second sandwichdirection) and intersecting with the first detection direction of theexternal force acting when the first sensor 12 outputs the electriccharge Qx. That is, the third sensor 14 is adapted to output positivecharge or negative charge in response to an external force.

The third sensor 14 has the fifth piezoelectric layer (second detectionplate) 141, the sixth piezoelectric layer (second detection plate) 143provided to be opposed to the fifth piezoelectric layer 141, and anoutput electrode layer 142 provided between the fifth piezoelectriclayer 141 and the sixth piezoelectric layer 143.

The fifth piezoelectric layer 141 is formed by a Y-cut crystal plate andhas an x-axis, a y-axis, and a z-axis orthogonal to one another. They-axis is an axis along the thickness direction of the fifthpiezoelectric layer 141, the x-axis is an axis along the longitudinaldirection in FIG. 4, and the z-axis is an axis along the paper depthdirection in FIG. 4.

The fifth piezoelectric layer 141 including crystal has advantageousproperties such as a wider dynamic range, higher rigidity, a highernatural frequency, and higher load bearing. Further, the Y-cut crystalplate generates electric charge for the external force (shear force)along the surface direction thereof.

When an external force along the positive direction of the x-axis isapplied to the surface of the fifth piezoelectric layer 141, electriccharge is induced within the fifth piezoelectric layer 141 due to thepiezoelectric effect. As a result, positive charge collects near thesurface at the output electrode layer 142 side of the fifthpiezoelectric layer 141, and negative charge collects near the surfaceat the ground electrode layer 11 side of the fifth piezoelectric layer141. Similarly, when an external force along the negative direction ofthe x-axis is applied to the surface of the fifth piezoelectric layer141, negative charge collects near the surface at the output electrodelayer 142 side of the fifth piezoelectric layer 141, and positive chargecollects near the surface at the ground electrode layer 11 side of thefifth piezoelectric layer 141.

The sixth piezoelectric layer 143 is also formed by a Y-cut crystalplate and has an x-axis, a y-axis, and a z-axis orthogonal to oneanother. The y-axis is an axis along the thickness direction of thesixth piezoelectric layer 143, the x-axis is an axis along thelongitudinal direction in FIG. 4, and the z-axis is an axis along thepaper depth direction in FIG. 4.

Like the fifth piezoelectric layer 141, the sixth piezoelectric layer143 including crystal has advantageous properties such as a widerdynamic range, higher rigidity, a higher natural frequency, and higherload bearing, and the Y-cut crystal plate generates electric charge forthe external force (shear force) along the surface direction thereof.

When an external force along the positive direction of the x-axis isapplied to the surface of the sixth piezoelectric layer 143, electriccharge is induced within the sixth piezoelectric layer 143 due to thepiezoelectric effect. As a result, positive charge collects near thesurface at the output electrode layer 142 side of the sixthpiezoelectric layer 143, and negative charge collects near the surfaceat the ground electrode layer 11 side of the sixth piezoelectric layer143. Similarly, when an external force along the negative direction ofthe x-axis is applied to the surface of the sixth piezoelectric layer143, negative charge collects near the surface at the output electrodelayer 142 side of the sixth piezoelectric layer 143, and positive chargecollects near the surface at the ground electrode layer 11 side of thesixth piezoelectric layer 143.

In the charge output element 10, as seen from the lamination directionLD, the respective x-axes of the first piezoelectric layer 121 and thesecond piezoelectric layer 123 intersect with the respective x-axes ofthe fifth piezoelectric layer 141 and the sixth piezoelectric layer 143.Further, as seen from the lamination direction LD, the respective z-axesof the first piezoelectric layer 121 and the second piezoelectric layer123 intersect with the respective z-axes of the fifth piezoelectriclayer 141 and the sixth piezoelectric layer 143.

The output electrode layer 142 has a function of outputting positivecharge or negative charge generated within the fifth piezoelectric layer141 and the sixth piezoelectric layer 143 as electric charge Qy. Asdescribed above, when an external force along the positive direction ofthe x-axis is applied to the surface of the fifth piezoelectric layer141 or the surface of the sixth piezoelectric layer 143, positive chargecollects near the output electrode layer 142. As a result, positivecharge Qy is output from the output electrode layer 142. On the otherhand, when an external force along the negative direction of the x-axisis applied to the surface of the fifth piezoelectric layer 141 or thesurface of the sixth piezoelectric layer 143, negative charge collectsnear the output electrode layer 142. As a result, negative charge Qy isoutput from the output electrode layer 142.

As described above, in the charge output element 10, the first sensor12, the second sensor 13, and the third sensor 14 are laminated so thatthe force detection directions of the respective sensors may beorthogonal to one another. Thereby, the respective sensors may induceelectric charge in response to force components orthogonal to oneanother. Accordingly, the charge output element 10 may output threeelectric charges Qx, Qy, Qz in response to the respective externalforces along the x-axis, the y-axis, and the z-axis.

Further, as described above, the charge output element 10 may output theelectric charge Qz, however, it is preferable not to use the electriccharge Qz for obtaining the respective external forces in the forcedetector 1. That is, it is preferable to use the force detector 1 as anapparatus that detects shear force not detecting compression and tensionforce. Thereby, noise components due to temperature changes of the forcedetector 1 may be reduced.

Here, as the reason why it is preferable not to use the electric chargeQz, the case where the force detector 1 is used for an industrial robothaving an arm to which an end effector is attached will be explained asan example. In this case, by heat transfer from heat source such asmotors provided in the arm and the end effector, the first base part 2or the second base part 3 are heated and thermally expanded, anddeformed. Due to the deformation, the pressurization on the chargeoutput elements 10 changes from a predetermined values. The electriccharge Qz contains the pressurization changes on the charge outputelements 10 as noise components due to the temperature changes of theforce detector 1 to the degree of significant influence.

On this account, the charge output elements 10 detect only the electriccharges Qx, Qy generated by application of shear forces without usingthe electric charge Qz generated by application of compression andtension forces, and thereby, may be harder to be influenced by thetemperature variations.

Note that the output electric charge Qz is used for e.g., adjustment ofthe pressurization by the pressurization bolts 71.

Further, in the embodiment, all of the above described respectivepiezoelectric layers (first piezoelectric layer 121, secondpiezoelectric layer 123, third piezoelectric layer 131, fourthpiezoelectric layer 133, fifth piezoelectric layer 141, and sixthpiezoelectric layer 143) are formed using crystal, however, therespective piezoelectric layers may have configurations using otherpiezoelectric materials than crystal. The other piezoelectric materialsthan crystal include e.g., topaz, barium titanate, lead titanate, leadtitanate zirconate (PZT: Pb(Zr,Ti)O₃), lithium niobate, lithiumtantalate, etc. However, it is preferable that the respectivepiezoelectric layers have configurations using crystal. This is becausethe piezoelectric layers including crystal have advantageous propertiessuch as wider dynamic ranges, higher rigidity, higher naturalfrequencies, and higher load bearing.

Furthermore, as described above, the first base part 2 and the secondbase part 3 are secured by the pressurization bolts 71.

The securement by the pressurization bolts 71 is performed by insertingthe pressurization bolts 71 from the side walls 33 side of the secondbase part 3 toward the convex portions 23 of the first base part 2, andscrewing external threads (not shown) of the pressurization bolts 71 inthe internal threads 241 formed in the first base part 2 in such a statethat each sensor device 6 is arranged between the top surface 231 andthe inner wall surface 331. In this manner, to the charge outputelements 10, pressure having predetermined magnitude, i.e.,pressurization is applied by the first base part 2 and the second basepart 3 with respect to each package 60 housing the charge output element10.

Note that the first base part 2 and the second base part 3 are securedby the two pressurization bolts 71 to be displaceable (movable) in apredetermined amount with respect to each other. The first base part 2and the second base part 3 are secured to be displaceable in thepredetermined amount with respect to each other, and thereby, when anexternal force (shear force) is applied to the force detector 1 and theshear force acts on the charge output elements 10, friction forces arereliably generated between the layers forming the charge output elements10 and electric charge may be reliably detected. Further, thepressurization directions by the respective pressurization bolts 71 aredirections in parallel to the lamination direction LD.

As shown in FIG. 5, regarding the charge output element 10 having theabove described configuration, the lamination directions LD is tilted ata tilt angle ε with respect to the α-axis. Specifically, the x-axis ofthe first sensor 12 and the z-axis of the third sensor 14 are tilted atthe tilt angle ε with respect to the α-axis. Therefore, in theembodiment, the α-axis is a bisector that bisects the angle formed bythe charge output element 10 of the sensor device 6A and the chargeoutput element 10 of the sensor device 6B.

Further, as shown in FIG. 6, supposing that the angle formed by thex-axis of the first sensor 12 and the bottom plate 22 of the first basepart 2 is η, each charge output element 10 is permitted to tilt to thedegree that the angle η satisfies 0°≤η≤90°. Note that FIG. 6 is adiagram as seen from an arrow D in FIG. 5, and the charge output element10 tilted at the angle η with respect to the α-axis (the lower surface221 of the bottom plate 22) is shown by hypothetical lines (dashedtwo-dotted lines).

Next, the conversion output circuit 90 a, the conversion output circuit90 b, and the conversion output circuit 90 c of the respective analogcircuit boards 4 will be described in detail.

Conversion Output Circuits

As shown in FIG. 3, each conversion output circuit 90 c converts one ofelectric charges Qx1 to Qx4 (Qx) into one of the voltages Vx1 to Vx4(representatively referred to as “voltage Vx”), each conversion outputcircuit 90 b converts one of electric charges Qz1 to Qz4 (Qz) into oneof the voltages Vz1 to Vz4 (representatively referred to as “voltageVz”), and each conversion output circuit 90 a converts one of electriccharges Qy1 to Qy4 (Qy) into one of the voltages Vy1 to Vy4(representatively referred to as “voltage Vy”).

As below, the configurations etc. of the conversion output circuits 90a, 90 b, 90 c will be described in detail, and the conversion outputcircuit 90 c will be representatively explained because the respectiveconversion output circuits 90 a, 90 b, 90 c have the same configuration.

As shown in FIG. 3, the conversion output circuit 90 c has a function ofconverting the electric charge Qx output from the charge output element10 into the voltage Vx and outputting the voltage Vx. The conversionoutput circuit 90 c has an operational amplifier 91, a capacitor 92, anda switching element 93. The first input terminal (negative input) of theoperational amplifier 91 is connected to the output electrode layer 122of the charge output element 10, and the second input terminal (positiveinput) of the operational amplifier 91 is grounded to the ground(reference potential point). Further, the output terminal of theoperational amplifier 91 is connected to the external force detectioncircuit 40. The capacitor 92 is connected between the first inputterminal and the output terminal of the operational amplifier 91. Theswitching element 93 is connected between the first input terminal andthe output terminal of the operational amplifier 91 andparallel-connected to the capacitor 92. Furthermore, the switchingelement 93 is connected to a drive circuit (not shown) and the switchingelement 93 executes switching operation according to on/off signals fromthe drive circuit.

When the switching element 93 is off, the electric charge Qx output fromthe charge output element 10 is accumulated in the capacitor 92 havingcapacitance Cl and output to the external force detection circuit 40 asthe voltage Vx. Then, when the switching element 93 is turned on,terminals of the capacitor 92 are short-circuited. As a result, theelectric charge Qx accumulated in the capacitor 92 is discharged to bezero coulomb and the voltage V output to the external force detectioncircuit 40 becomes zero volt. Turning on of the switching element 93 isreferred to as resetting of the conversion output circuit 90 c. Notethat the voltage Vx output from the ideal conversion output circuit 90 cis proportional to the amount of accumulation of the electric charge Qxoutput from the charge output element 10.

The switching element 93 is e.g., a MOSFET (Metal Oxide SemiconductorField Effect Transistor), a semiconductor switch, an MEMS switch, or thelike. The switch is smaller and lighter than a mechanical switch, andadvantageous to reduction in size and weight of the force detector 1. Asbelow, as a representative example, the case where the MOSFET is used asthe switching element 93 will be explained. Note that, as shown in FIG.3, the switch is mounted on the conversion output circuit 90 c and theconversion output circuits 90 a, 90 b, and may be further mounted on theAD converter 401.

The switching element 93 has a drain electrode, a source electrode, anda gate electrode. One of the drain electrode and the source electrode ofthe switching element 93 is connected to the first input terminal of theoperational amplifier 91 and the other of the drain electrode and thesource electrode is connected to the output terminal of the operationalamplifier 91. Further, the gate electrode of the switching element 93 isconnected to the drive circuit (not shown).

To the switching elements 93 of the respective conversion outputcircuits 90 a, 90 b, 90 c, the same drive circuits may be connected orrespective different drive circuits may be connected. To the respectiveswitching elements 93, all of synchronized on/off signals are input fromthe drive circuits. Thereby, the operations of the switching elements 93of the respective conversion output circuits 90 a, 90 b, 90 c aresynchronized. That is, the on/off timings of the switching elements 93of the respective conversion output circuits 90 a, 90 b, 90 c coincide.

Next, the external force detection circuit 40 of the digital circuitboard 5 will be described in detail.

External Force Detection Circuit

The external force detection circuit 40 has a function of detectingapplied external forces based on the voltages Vy1, Vy2, Vy3, Vy4 outputfrom the respective conversion output circuits 90 a, the voltages Vz1,Vz2, Vz3, Vz4 output from the respective conversion output circuits 90b, and the voltages Vx1, Vx2, Vx3, Vx4 output from the respectiveconversion output circuits 90 c.

The external force detection circuit 40 has the AD converter 401connected to the conversion output circuits (conversion circuits) 90 a,90 b, 90 c and the calculation part (calculation circuit) 402 connectedto the AD converter 401.

The AD converter 401 has a function of converting the voltages Vx1, Vy1,Vz1, Vx2, Vy2, Vz2, Vx3, Vy3, Vz3, Vx4 Vy4, Vz4 from analog signals todigital signals. The voltages Vx1, Vy1, Vz1, Vx2, Vy2, Vz2, Vx3, Vy3,Vz3, Vx4 Vy4, Vz4 digitally converted by the AD converter 401 are inputto the calculation part 402.

The calculation part 402 performs respective processing of e.g.,correction for eliminating differences in sensitivity among therespective conversion output circuits 90 a, 90 b, 90 c etc. on thedigitally converted voltages Vx, Vy, Vz. Then, the calculation part 402outputs three signals proportional to the amounts of accumulation of theelectric charges Qx, Qy, Qz output from the charge output elements 10.

Force Detection (Force Detection Method) in α-Axis, β-Axis, γ-AxisDirections

As described above, each charge output element 10 is placed so that thelamination direction LD and the sandwich direction SD may be in parallelto the first base part 2 (bottom plate 22) and orthogonal to the normalNL₂ of the upper surface 321 (see FIG. 1).

Further, a force F_(A) in the α-axis direction, a force F_(B) in theβ-axis direction, and a force F_(C) in the γ-axis direction may berespectively expressed by the following expressions (1), (2), and (3).“fx₁₋₁” in the expressions (1) to (3) is a force applied in the x-axisdirection of the first sensor 12 (first detection plate) of the sensordevice 6A, i.e., a force obtained from the electric charge Qx1 (firstoutput), and “fx₁₋₂” is a force applied in the x-axis direction of thethird sensor 14 (second detection plate), i.e., a force obtained fromthe electric charge Qy1 (second output). Furthermore, “fx₂₋₁” is a forceapplied in the x-axis direction of the first sensor 12 (first detectionplate) of the sensor device 6B, i.e., a force obtained from the electriccharge Qx2 (third output), and “fx₂₋₂” is a force applied in the x-axisdirection of the third sensor 14 (second detection plate), i.e., a forceobtained from the electric charge Qy2 (fourth output).F _(A) =fx ₁₋₁·cos ƒ·cos ε−fx ₁₋₂·sin ƒ·cos ε−fx ₂₋₁·cos η·cos ε+fx₂₋₂·sin η·cos ε  (1)F _(B) =−fx ₁₋₁·cos η·sin ε+fx ₁₋₂·sin η·sin ε−fx ₂₋₁·cos η·sin ε+fx₂₋₂·sin η·sin ε  (2)F _(C) =−fx ₁₋₁·sin η−fx ₁₋₂·cos η−fx ₂₋₁·sin η−fx ₂₋₂·cos η  (3)

For example, in the case of the force detector 1 having theconfiguration shown in FIGS. 1 and 2, ε is 45° and η is 0°. Byassignment of 45° to ε and 0° to η in the expressions (1) to (3), theforces F_(A) to F_(C) are expressed as follows.F _(A) =fx ₁₋₁/√2−fx ₂₋₁/√2F _(B) =−fx ₁₋₁/√2−fx ₂₋₁/√2F _(C) =−fx ₁₋₂ −fx ₂₋₂

As described above, in the force detector 1, when the forces F_(A) toF_(C) are detected, the detection may be performed without using thesecond sensor 13 (electric charge Qz) easily influenced by temperaturevariations, i.e., with noise easily superimposed thereon. Therefore, theforce detector 1 is an apparatus harder to be influenced by thetemperature variations in which, for example, the influence is reducedto a twentieth part or less of that in a force detector of related art.Thereby, the force detector 1 may detect the forces F_(A) to F_(C)accurately and stably even under environments with severe temperaturechanges.

Note that the translational forces F_(A) to F_(C) and rotational forcesM_(A) to M_(C) of the whole force detector 1 in the embodiment arecalculated based on the electric charges from the respective chargeoutput elements 10. Further, the four charge output elements 10 areprovided in the embodiment, however, it is possible to calculate therotational forces M_(A) to M_(C) if at least three charge outputelements 10 are provided.

The force detector 1 having the above described configuration has atotal weight lighter than 1 kg. Thereby, the load on the wrist to whichthe weight of the force detector 1 is attached may be reduced and thevolume of the actuator for driving the wrist may be made smaller, andthus, the wrist may be designed to be smaller. Furthermore, the weightof the force detector 1 is lighter than 20% of the maximum capacitytransportation by the robot arm. Thereby, the robot arm to which theweight of the force detector 1 is attached may be controlled moreeasily.

The invention has a feature in the configuration of the package 60housing the above described charge output element 10. As below, thepackage 60 will be described in detail.

FIG. 7 is an enlarged longitudinal section view of the sensor device 6.In FIG. 7, illustration of the analog circuit board 4 is omitted.Further, for convenience of explanation, in FIG. 7, upside is referredto as “upper” or “above” and the downside is referred to as “lower” or“below”.

Package

As shown in FIG. 7, the package 60 has a bottom plate member (firstmember) 61, a lid member (second member) provided to face the bottomplate member 61, and a side wall member (third member) 67 that connectsthe bottom plate member 61 and the lid member 62. By the package 60, thecharge output element 10 is air-tightly sealed and shielded from outsideair, and thereby, the output electric charge is prevented fromunintendedly leaking due to moisture or the like.

The bottom plate member 61 has a flat plate shape and is provided incontact with the top surface 231 of the convex portion 23 of the firstbase part 2. The bottom plate member 61 has a function of transmittingthe external force applied to the first base part 2 to the charge outputelement 10.

The plan view shape of the bottom plate member 61 has a shapecorresponding to the top surface 231 of the convex portion 23 and isformed so that the plane area may be slightly larger than the area ofthe top surface 231. Therefore, in a state in which the sensor device 6is fixed between the first base part 2 and the second base part 3, anouter edge portion 611 of the bottom plate member 61 projects from theconvex portion 23 toward the side.

Note that, as shown in FIG. 7, it is preferable that the plane area ofthe bottom plate member 61 has a size to cover the charge output element10, however, may have a smaller shape than the charge output element 10or may have an equal size.

In the embodiment, the plan view shape of the bottom plate member 61 isa rectangular shape, however, may be another polygonal shape than therectangular shape, a circular shape, an oval shape, or the like.Further, the corner parts of the bottom plate member 61 may be roundedor obliquely cut out.

To the outer edge portion 611 of the bottom plate member 61, the sidewall member 67 forming a rectangular tubular shape is bonded. A concaveportion 65 is defined by the side wall member 67 and the bottom platemember 61, and the charge output element 10 is provided apart from theinner wall surface of the side wall member 67 within the concave portion65.

The side wall member 67 has a lower side portion 671 bonded to thebottom plate member 61, and an upper side portion 672 provided on thelower side portion 671 and having a through hole with a cross-sectionarea larger than a cross-section area of a through hole of the lowerside portion 671. Therefore, in a state in which the lower side portion671 and the upper side portion 672 are bonded, part of the upper surfaceof the lower side portion 671 is exposed within the through hole of theupper side portion 672.

On the inner wall surface of the lower side portion 671, a step portion673 formed by increasing the cross-section area of the through hole inthe middle of the height direction is provided. To the step portion 673,the bottom plate member 61 is bonded apart from the inner wall surfaceof the side wall member 67 (lower side portion 671).

Further, in predetermined locations of the lower side portion 671, fourterminals 66 are provided over the upper surface, the outer wallsurface, and the lower surface of the lower side portion 671. An upperportion 662 of the terminal 66 is exposed within the through hole(convex portion 65) of the upper side portion 672, and bonded to aconnecting portion 64 in the upper portion 662. Thereby, the terminal 66is electrically connected to the charge output element 10 via theconnecting portion 64. Further, a lower portion 661 of the terminal 66is exposed from the lower surface of the side wall member 67 to theoutside, and bonded to the analog circuit board 4 via wiring (notshown).

Note that it is only necessary that the terminal 66 has conductivity.For example, the terminal may be formed by stacking respective films ofnickel, gold, silver, copper on a metallization layer (foundation layer)of chromium, tungsten, or the like. Further, the connecting portion 64may be formed using e.g., conductive paste such as Ag paste, Cu paste,or Au paste, and preferably formed using the Ag paste because the pasteis easily available and advantageous in handling.

On the upper surface of the side wall member 67 (upper side portion672), the lid member 62 is bonded via sealant 63 including e.g., gold,titanium, aluminum, copper, iron, or an alloy containing them.

The lid member 62 is provided in contact with the second base part 3,and has a function of transmitting the external force applied to thesecond base part 3 to the charge output element 10.

The lid member 62 is formed to have a dish shape as a whole by bending(or curving) deformation of a flat plate-like member so that the centerportion 625 may project from an outer periphery portion 626 toward thesecond base part 3. According to the configuration, the center portion625 of the lid member 62 is in contact with the inner wall surface 331of the second base part 3. Note that the plan view shape of the centerportion 625 is not particularly limited, however, in the embodiment, isa shape corresponding to the plan view shape of the charge outputelement 10, i.e., a rectangular shape.

The thicknesses of the bottom plate member 61 and the lid member 62 maybe different from each other or the same.

In the package 60 having the configuration, a longitudinal elasticmodulus (first longitudinal elastic modulus) of at least a part of thebottom plate member 61 and a longitudinal elastic modulus (secondlongitudinal elastic modulus) of at least apart of the lid member 62 arerespectively lower than a longitudinal elastic modulus (thirdlongitudinal elastic modulus) of the side wall member 67.

Accordingly, the bottom plate member 61 and the lid member 62 are moreelastically deformable when stress is applied thereto than the side wallmember 67. Thereby, even when external forces are repeatedly applied tothe first base part 2 and the second base part 3, the bottom platemember 61 and the lid member 62 may be deformed in response to theexternal forces. Therefore, breakage of the bottom plate member 61 andthe lid member 62 may be reduced. Thus, the force detector 1 isadvantageous in reliability over a long period. Further, when the sensordevice 6 is fixed between the first base part 2 and the second base part3 by the pressurization bolts 71, if pressure beyond necessity isapplied to the bottom plate member 61 and the lid member 62 by fasteningof the pressurization bolts 71, breakage of the bottom plate member 61and the lid member 62 may be reduced.

As described above, the charge output element 10 and the bottom platemember 61 are provided apart from the inner wall surface of the sidewall member 67. Accordingly, even when the charge output element 10 andthe bottom plate member 61 are deformed, contact with the side wallmember 67 may be avoided. Thereby, also, breakage of the charge outputelement 10 and the bottom plate member 61 may be reduced. From theviewpoint, the force detector 1 is also advantageous in reliability overa long period.

Further, in the bottom plate member 61, only a part thereof(particularly, only the part in contact with the convex portion 23) mayhave the first longitudinal elastic modulus, however, it is preferablethat the member has the first longitudinal elastic modulus over thewhole. Thereby, the bottom plate member 61 may be formed by a singlemember and a single material, and the longitudinal elastic modulus andthe mechanical strength may be homogenized over the whole bottom platemember 61. Accordingly, breakage of the bottom plate member 61 due tothe external force applied to the first base part 2 may be reduced morereliably, and the external force may be transmitted to the charge outputelement 10 via the bottom plate member 61 more accurately.

In the lid member 62, a part thereof (particularly, only the centerportion 625) may have the second longitudinal elastic modulus, however,it is preferable that the member has the second longitudinal elasticmodulus over the whole. Thereby, the lid member 62 may be formed by asingle member and a single material, and the longitudinal elasticmodulus and the mechanical strength may be homogenized over the whole ofthe lid member 62. Particularly, the lid member 62 has the shape suchthat the center portion 625 and the outer periphery portion 626 areconnected by an inclined portion (dish shape), and, when the lid memberis formed by a single member and a single material, rapid changes inmechanical strength in the bonded parts of the respective portions maybe reduced. Accordingly, breakage of the lid member 62 due to theexternal force applied to the second base part 3 may be reduced morereliably, and the external force may be transmitted to the charge outputelement 10 via the lid member 62 more accurately.

Further, the difference between the first longitudinal elastic modulusand the second longitudinal elastic modulus is preferably a tenth partor less, more preferably a twentieth part or less, even more preferablya thirtieth part or less of the first longitudinal elastic modulus.Thereby, concentration of stress on only one of the bottom plate member61 and the lid member 62 may be avoided. Accordingly, the externalforces applied to the first base part 2 and second base part 3 aredispersed, and thereby, breakage of the bottom plate member 61 and thelid member 62 may be reduced more reliably.

Specifically, the first longitudinal elastic modulus is preferably from50 GPa to 300 GPa, more preferably from 100 GPa to 250 GPa, and evenmore preferably from 120 GPa to 200 GPa. If the first longitudinalelastic modulus is within the ranges, the bottom plate member 61 hasmoderate rigidity and is efficiently elastically deformed. Accordingly,even when external forces are repeatedly applied to the first base part2, the bottom plate member 61 is deformed in response to the externalforces more precisely. Therefore, breakage of the bottom plate member 61due to the external force applied to the first base part 2 may bereduced more reliably, and the external force may be transmitted to thecharge output element 10 via the bottom plate member 61 more accurately.

Further, the second longitudinal elastic modulus is preferably from 50GPa to 300 GPa, more preferably from 100 GPa to 250 GPa, and even morepreferably from 120 GPa to 200 GPa. If the second longitudinal elasticmodulus is within the ranges, the lid member 62 has moderate rigidityand is efficiently elastically deformed. Accordingly, even when externalforces are repeatedly applied to the second base part 3, the lid member62 is deformed in response to the external forces more precisely.Therefore, breakage of the lid member 62 due to the external forceapplied to the second base part 3 may be reduced more reliably, and theexternal force may be transmitted to the charge output element 10 viathe lid member 62 more accurately.

Furthermore, the third longitudinal elastic modulus is preferably from200 GPa to 500 GPa, more preferably from 250 GPa to 480 GPa, and evenmore preferably from 300 GPa to 450 GPa. If the third longitudinalelastic modulus is within the ranges, the side wall member 67 hassufficient rigidity, and the mechanical strength as the whole package 60may be sufficiently secured. Accordingly, even when external forces arerepeatedly applied thereto, damage by the deformation of the package 60is harder to be caused, and the charge output element 10 housed insidemay be protected more reliably.

Note that the third longitudinal elastic modulus refers to alongitudinal elastic modulus in the whole side wall member 67 includingthe plurality of members.

Further, it is preferable that coefficients of thermal expansion of thebottom plate members 61, the lid members 62, and the side wall members67 are respectively as close to coefficients of thermal expansion of thepiezoelectric layers 121, 123, 131, 133, 141, 143 of the charge outputelements 10 as possible. Thereby, even when the piezoelectric layers121, 123, 131, 133, 141, 143 expand or contract due to temperaturechanges, the bottom plate members 61, the lid members 62, and the sidewall members 67 expand or contract equally to the piezoelectric layers.Accordingly, compression stress or tension stress generated in thepiezoelectric layers 121, 123, 131, 133, 141, 143 due to the differencesin degree of thermal deformation from the bottom plate members 61, thelid members 62, and the side wall members 67 may be further reduced.Therefore, output of unnecessary electric charges due to temperaturechanges may be further reduced, and thus, the force detector 1 mayperform force detection with higher accuracy.

In the embodiment, the piezoelectric layers 121, 123, 131, 133, 141, 143include crystal, and the coefficients of thermal expansion from 25° C.to 200° C. in the x-axis directions are 13.4×10⁻⁶ (1/K), thecoefficients of thermal expansion from 25° C. to 200° C. in the y-axisdirections are 13.4×10⁻⁶ (1/K), and the coefficients of thermalexpansion from 25° C. to 200° C. in the z-axis directions are 7.8×10⁻⁶(1/K).

Therefore, when the piezoelectric layers 121, 123, 131, 133, 141, 143include crystal, the coefficients of thermal expansion from 25° C. to200° C. of the respective constituent materials for the bottom platemembers 61, the lid members 62, and the side wall members 67 arepreferably from 1×10⁻⁶ (1/K) to 1×10⁻⁷ (1/K) and more preferably from3×10⁻⁶ (1/K) to 9×10⁻⁶ (1/K). Thereby, compression stress or tensionstress generated in the respective piezoelectric layers 121, 123, 131,133, 141, 143 due to the differences in degree of thermal deformationamong the bottom plate members 61, the lid members 62, and the side wallmembers 67 may be further reduced.

The constituent material of the bottom plate member 61 and theconstituent material of the lid member 62 may be the same or different,but preferably the same. Thereby, the longitudinal elastic moduli andthe coefficients of thermal expansion of the bottom plate member 61 andthe lid member 62 may be made nearly equal. Accordingly, breakage of thebottom plate member 61 and the lid member 62 due to the applied externalforce may be reduced more effectively. Further, compression stress ortension stress generated in the respective piezoelectric layers 121,123, 131, 133, 141, 143 due to the differences in degree of thermaldeformation between the bottom plate members 61 and the lid members 62may be further reduced. Furthermore, the constituent material of thebottom plate member 61 and the constituent material of the lid member 62are the same, and material properties including e.g., lateral elasticmodulus and hardness may be made nearly equal. Thereby, concentration ofthe applied external force on only one of the bottom plate member 61 andthe lid member 62 may be avoided, and unintended deformation andbreakage of them may be reduced especially effectively.

Here, in this specification, the same constituent materials include notonly materials having completely the same composition ratio but alsomaterials having slightly different composition ratios, but havingnearly equal properties (longitudinal elastic moduli and coefficients ofthermal expansion).

The constituent materials of the bottom plate member 61 and the lidmember 62 that satisfy the above described conditions include variousmetal materials, e.g., stainless steel, kovar, copper, iron, carbonsteel, titanium, etc. Of them, particularly, kovar is preferable.Thereby, the bottom plate member 61 has relatively high rigidity and ismoderately elastically deformed by stress application. Accordingly, thebottom plate member 61 may accurately transmit the external forceapplied to the first base part 2 to the charge output element 10, andbreakage due to the external force may be further reduced. Kovar is alsopreferable in the viewpoint of advantageous molding processability.

The coefficient of thermal expansion from 25° C. to 200° C. of kovar is5.2×10⁻⁶ (1/K) and a value closer to the coefficient of thermalexpansion of crystal. Accordingly, as in the embodiment, when thepiezoelectric layers 121, 123, 131, 133, 141, 143 of the charge outputelements 10 include crystal, compression stress or tension stressgenerated in the respective piezoelectric layers 121, 123, 131, 133,141, 143 due to the differences in degree of thermal deformation betweenthe bottom plate members 61 and the lid members 62 may be particularlyeffectively suppressed.

On the other hand, the constituent material of the side wall member 67that satisfies the above described conditions is not particularlylimited. However, an insulating material is preferable, a materialcontaining various kinds of ceramics such as oxide-based ceramics ofalumina, zirconia, or the like, carbide-based ceramics of siliconcarbide or the like, nitride-based ceramics of silicon nitride or thelike is more preferable, and a material consisting primarily of variouskinds of ceramics is even more preferable. The ceramics has moderaterigidity and advantageous insulation properties. Accordingly, damage dueto deformation of the package 60 is harder to be caused and the chargeoutput element 10 housed inside may be protected more reliably, andshort circuit between the terminals 66 may be avoided more reliably.Further, the processing accuracy of the side wall member 67 may befurther improved.

Further, it is preferable that the constituent material of the side wallmember 67 primarily contains ceramics having the coefficient of thermalexpansion that satisfies the above described ranges. Thereby,compression stress or tension stress generated in the piezoelectriclayers 121, 123, 131, 133, 141, 143 due to the differences in degree ofthermal deformation from the side wall members 67 may be furtherreduced.

Note that, in the embodiment, the explanation that the first member ofthe housing part (package) is the bottom plate member, the second memberis the lid member, and the third member is the side wall member is made,however, the first member refers to a member located between thepiezoelectric element and the first base part in a region where thepiezoelectric element and the first base part overlap as seen from thethickness direction of the force detector. Further, the second memberrefers to a member located between the piezoelectric element and thesecond base part in a region where the piezoelectric element and thesecond base part overlap as seen from the thickness direction of theforce detector. Furthermore, the third member refers to a memberconnecting the first member and the second member, preferably refers toa member provided not in contact with the piezoelectric element (chargeoutput element) or the first base part and the second base part.

2. Single-Arm Robot

Next, a single-arm robot as an embodiment of a robot of the inventionwill be explained with reference to FIG. 8.

FIG. 8 shows an example of the single-arm robot using the force detectoraccording to the invention. A single-arm robot 500 in FIG. 8 has a base510, an arm 520, an end effector 530 provided at the distal end side ofthe arm 520, and the force detector 1 provided between the arm 520 andthe end effector 530. Note that, as the force detector 1, the same oneas those in the above described respective embodiments is used.

The base 510 has a function of housing an actuator (not shown) thatgenerates power for rotating the arm 520, a control unit (not shown)that controls the actuator, etc. Further, the base 510 is fixed to afloor, a wall, a ceiling, a movable carriage, or the like, for example.

The arm 520 has a first arm element 521, a second arm element 522, athird arm element 523, a fourth arm element 524, and a fifth arm 525,and is formed by rotatably connecting the adjacent arm elements. The arm520 is driven by composite rotation or bending around the connectingparts of the respective arm elements under control of the control unit.

The end effector 530 has a function of grasping an object. The endeffector 530 has a first finger 531 and a second finger 532. The endeffector 530 reaches a predetermined operation position by the drivingof the arm 520, then, the separated distance between the first finger531 and the second finger 532 is adjusted, and thereby, the object maybe grasped.

The end effector 530 is a hand here, however, not limited to that in theinvention. Other examples of the end effector include a part testingtool, a part carrying tool, a part processing tool, a part assemblytool, a measuring instrument, etc., for example. This applies to the endeffectors in the other embodiments.

The force detector 1 has a function of detecting an external forceapplied to the end effector 530. The force detected by the forcedetector 1 is fed back to the control unit of the base 510, and thereby,the single-arm robot 500 may execute more precise work. Further, thesingle-arm robot 500 may sense the end effector 530 in contact with anobstacle or the like using the force detected by the force detector 1.Accordingly, the obstacle avoidance operation, the object damageavoidance operation, etc. that have been difficult by the positioncontrol in related art may be easily performed, and the single-arm robot500 may execute work more safely.

Note that, in the illustrated configuration, the arm 520 has the fivearm elements in total, however, the invention is not limited to that.The cases where the arm 520 has a single arm element, two to four armelements, and six or more arm elements fall within the scope of theinvention.

3. Multi-Arm Robot

Next, a multi-arm robot as an embodiment of the robot according to theinvention will be explained with reference to FIG. 9.

FIG. 9 shows an example of the multi-arm robot using the force detectoraccording to the invention. A multi-arm robot 600 in FIG. 9 has a base610, a first arm 620, a second arm 630, a first end effector 640 aprovided at the distal end side of the first arm 620, a second endeffector 640 b provided at the distal end side of the second arm 630,and force detectors 1 provided between the first arm 620 and the firstend effector 640 a and between the second arm 630 and the second endeffector 640 b. Note that, as the force detectors 1, the same ones asthose in the above described respective embodiments are used.

The base 610 has a function of housing actuators (not shown) thatgenerate power for rotating the first arm 620 and the second arm 630, acontrol unit (not shown) that controls the actuators, etc. Further, thebase 610 is fixed to a floor, a wall, a ceiling, a movable carriage, orthe like, for example.

The first arm 620 is formed by rotatably connecting a first arm element621 and a second arm element 622. The second arm 630 is formed byrotatably connecting a first arm element 631 and a second arm element632. The first arm 620 and the second arm 630 are driven by compositerotation or bending around the connecting parts of the respective armelements under control of the control unit.

The first and second end effectors 640 a and 640 b have functions ofgrasping objects. The first end effector 640 a has a first finger 641 aand a second finger 642 a. The second end effector 640 b has a firstfinger 641 b and a second finger 642 b. The first end effector 640 areaches a predetermined operation position by the driving of the firstarm 620, then, the separated distance between the first finger 641 a andthe second finger 642 a is adjusted, and thereby, the object may begrasped. Similarly, the second end effector 640 b reaches apredetermined operation position by the driving of the second arm 630,then, the separated distance between the first finger 641 b and thesecond finger 642 b is adjusted, and thereby, the object may be grasped.

The force detectors 1 have functions of detecting external forcesapplied to the first and second end effectors 640 a and 640 b. Theforces detected by the force detectors 1 are fed back to the controlunit of the base 610, and thereby, the multi-arm robot 600 may executework more precisely. Further, the multi-arm robot 600 may sense thefirst and second end effectors 640 a and 640 b in contact with anobstacle or the like using the forces detected by the force detectors 1.Accordingly, the obstacle avoidance operation, the object damageavoidance operation, etc. that have been difficult by the positioncontrol in related art may be easily performed, and the multi-arm robot600 may execute work more safely.

Note that, in the illustrated configuration, the two arms are providedin total, however, the invention is not limited to that. The case wherethe multi-arm robot 600 has three or more arms falls within the scope ofthe invention.

4. Electronic Component Testing Apparatus and Electronic ComponentCarrying Apparatus

Next, an electronic component testing apparatus and an electroniccomponent carrying apparatus including the force detectors according tothe invention will be explained with reference to FIGS. 10 and 11.

FIG. 10 shows examples of the electronic component testing apparatus anda part carrying apparatus using the force detector according to theinvention. FIG. 11 shows an example of the electronic component carryingapparatus using the force detector according to the invention.

An electronic component testing apparatus 700 in FIG. 10 has a base 710and a support 720 stood on the side surface of the base 710. On theupper surface of the base 710, an upstream-side stage 712 u on which anelectronic component 711 to be tested is placed and carried and adownstream-side stage 712 d on which the electronic component 711 thathas been tested is placed and carried are provided. Further, an imagingunit 713 for confirmation of the orientation of the electronic component711 and a testing bench 714 on which the electronic component 711 is setfor testing of electrical characteristics are provided between theupstream-side stage 712 u and the downstream-side stage 712 d. Note thatexamples of the electronic component 711 include semiconductors,semiconductor wafers, display devices such as CLD and OLED, crystaldevices, various sensors, inkjet heads, various MEMS devices, etc.

On the support 720, a Y-stage 731 is provided movably in a direction(Y-direction) parallel to the upstream-side stage 712 u and thedownstream-side stage 712 d of the base 710 and an arm part 732 isextended from the Y-stage 731 in a direction (X-direction) toward thebase 710. Further, an X-stage 733 is provided movably in the X-directionon the side surface of the arm part 732. On the X-stage 733, an imagingcamera 734 and an electronic component carrying apparatus 740 includinga Z-stage movable in vertical directions (Z-directions) are provided. Agrasping part 741 that grasps the electronic component 711 is providedat the end side of the electronic component carrying apparatus 740.Furthermore, a force detector 1 is provided between the end of theelectronic component carrying apparatus 740 and the grasping part 741.In addition, a control unit 750 that controls the entire operation ofthe electronic component testing apparatus 700 is provided at the frontsurface side of the base 710. Note that, as the force detector 1, thesame one as the above described respective embodiments is used.

The electronic component testing apparatus 700 performs a test of theelectronic component 711 in the following manner. First, the electroniccomponent 711 to be tested is placed on the upstream-side stage 712 uand moved close to the testing bench 714. Then, the electronic componentcarrying apparatus 740 is moved to the position immediately above theelectronic component 711 placed on the upstream-side stage 712 u bymoving the Y-stage 731 and the X-stage 733. In this regard, the positionof the electronic component 711 may be confirmed using the imagingcamera 734. Then, the electronic component carrying apparatus 740 ismoved downward using the Z-stage within the electronic componentcarrying apparatus 740, the electronic component 711 is grasped by thegrasping part 741, and then, the electronic component carrying apparatus740 is moved to above the imaging unit 713 without change, and theorientation of the electronic component 711 is confirmed using theimaging unit 713. Then, the orientation of the electronic component 711is adjusted using a fine adjustment mechanism built in the electroniccomponent carrying apparatus 740. Then, the electronic componentcarrying apparatus 740 is moved onto the testing bench 714, and then,the electronic component 711 is set on the testing bench 714 by movingthe Z-stage within the electronic component carrying apparatus 740. Theorientation of the electronic component 711 is adjusted using the fineadjustment mechanism within the electronic component carrying apparatus740, and thereby, the electronic component 711 may be set in a properposition on the testing bench 714. Then, the electrical characteristicstest of the electronic component 711 using the testing bench 714 isended, and then, in turn, the electronic component 711 is removed fromthe testing bench 714, the electronic component carrying apparatus 740is moved onto the downstream-side stage 712 d by moving the Y-stage 731and the X-stage 733, and the electronic component 711 is placed on thedownstream-side stage 712 d. Finally, the downstream-side stage 712 d ismoved and the electronic component 711 that has been tested is carriedto a predetermined position.

FIG. 11 shows the electronic component carrying apparatus 740 includingthe force detector 1. The electronic component carrying apparatus 740has the grasping part 741, the six-axial force detector 1 connected tothe grasping part 741, a rotation shaft 742 connected to the graspingpart 741 via the six-axial force detector 1, and a fine adjustment plate743 rotatably attached to the rotation shaft 742. The fine adjustmentplate 743 is movable in the X-direction and the Y-direction while beingguided by a guide mechanism (not shown).

Further, a piezoelectric motor 744θ for rotation direction is mounted toface the end surface of the rotation shaft 742, and a drive convexportion (not shown) of the piezoelectric motor 744θ is pressed againstthe end surface of the rotation shaft 742. Accordingly, by activation ofthe piezoelectric motor 744θ, the rotation shaft 742 (and the graspingpart 741) can be rotated to an arbitrary angle in the θ-direction.Further, a piezoelectric motor 744 x for X-direction and a piezoelectricmotor 744 y for Y-direction are provided to face the fine adjustmentplate 743, and their drive convex portions (not shown) are pressedagainst the surface of the fine adjustment plate 743. Accordingly, byactivation of the piezoelectric motor 744 x, the fine adjustment plate743 (and the grasping part 741) may be moved to an arbitrary distance inthe X-direction, and similarly, by activation of the piezoelectric motor744 y, the fine adjustment plate 743 (and the grasping part 741) may bemoved to an arbitrary distance in the Y-direction.

The force detector 1 has a function of detecting an external forceapplied to the grasping part 741. The force detected by the forcedetector 1 is fed back to the control unit 750, and thereby, theelectronic component carrying apparatus 740 and the electronic componenttesting apparatus 700 may execute work more precisely. Further, thegrasping part 741 in contact with an obstacle or the like may be sensedusing the force detected by the force detector 1. Accordingly, theobstacle avoidance operation, the object damage avoidance operation,etc. that have been difficult by the position control in related art maybe easily performed, and the electronic component carrying apparatus 740and the electronic component testing apparatus 700 may execute work moresafely.

5. Part Processing Apparatus

Next, an embodiment of a part processing apparatus including the forcedetector according to the invention will be explained with reference toFIG. 12.

FIG. 12 shows an example according to the part processing apparatususing the force detector according to the invention. A part processingapparatus 800 in FIG. 12 has a base 810, a support 820 stood on theupper surface of the base 810, a feed mechanism 830 provided on the sidesurface of the support 820, a tool displacement unit 840 attached to thefeed mechanism 830 so as to move up and down, the force detector 1connected to the tool displacement unit 840, and a tool 850 attached tothe tool displacement unit 840 via the force detector 1. Note that, asthe force detector 1, the same one as those in the respectiveembodiments is used.

The base 810 is a bench for mounting and fixing a processed part 860.The support 820 is a column for fixing the feed mechanism 830. The feedmechanism 830 has a function of moving up and down the tool displacementunit 840. The feed mechanism 830 has a feed motor 831, and a guide 832that moves up and down the tool displacement unit 840 based on theoutput from the feed motor 831. The tool displacement unit 840 has afunction of causing displacement including rotation and vibration of thetool 850. The tool displacement unit 840 has a displacement motor 841, atool attachment part 843 provided at the end of the main shaft (notshown) connected to the displacement motor 841, and a holding part 842attached to the tool displacement unit 840 and holding the main shaft.The tool 850 is attached to the tool attachment part 843 of the tooldisplacement unit 840 via the force detector 1 and used for processingthe processed part 860 in response to the displacement caused by thetool displacement unit 840. The tool 850 is not particularly limited,however, e.g., a wrench, across slot screwdriver, a straight slotscrewdriver, a cutter, a circular saw, a nipper, a borer, a drill, amilling cutter, or the like.

The force detector 1 has a function of detecting an external forceapplied to the tool 850. The external force detected by the forcedetector 1 is fed back to the feed motor 831 and the displacement motor841, and thereby, the part processing apparatus 800 may execute partprocessing work more precisely. Further, the tool 850 in contact with anobstacle or the like may be sensed using the external force detected bythe force detector 1. Accordingly, when an obstacle or the like isbrought into contact with the tool 850, emergency stop may be executed,and the part processing apparatus 800 may execute safer part processingwork.

The force detector and the robot according to the invention have beenexplained according to the illustrated embodiments, however, theinvention is not limited to those and the configurations of therespective parts forming the force detector and the robot may bereplaced by any configurations having the same functions. Further, anyother configurations may be added to the embodiments.

In addition, the force detector and the robot according to the inventionmay be combinations of any two or more configurations (features) of theabove described respective embodiments.

Further, in the force detector according to the invention, the fourcharge output elements are provided, however, the number of chargeoutput elements is not limited to that. For example, the number ofcharge output elements may be one, two, three, or five or more.

Furthermore, in the invention, in place of the pressurization bolts,bolts not having the function of pressurizing the elements may be used,and a securing method using other than bolts may be employed.

The robot according to the invention is not limited to the armed robot(robot arm), but may be another type of robot including a scalar robot,a legged walking (running) robot, or the like, for example, as long asthe robot has an arm.

In addition, the force detector according to the invention may beapplied, not limited to the robot, the electronic component carryingapparatus, the electronic component testing apparatus, and the partprocessing apparatus, but to other apparatuses including other carryingapparatuses, other testing apparatuses, vehicles such as automobiles,motorbikes, airplanes, ships, and trains, mobile units such as bipedwalking robots and wheel moving robots, measurement devices such asvibration meters, acceleration meters, gravity meters, dynamometers,seismometers, and inclinometers, input devices, etc.

What is claimed is:
 1. A force detector comprising: a first base; asecond base facing the first base; and a sensor that is disposed betweenthe first base and the second base, the sensor being configured with: aside wall having a terminal; a sensor plate that is connected to one endof the side wall; a lid that is connected to the other end of the sidewall so that an inner space is configured by the side wall, the sensorplate, and the lid; a charge output element that is disposed in theinner space and that outputs a signal in response to an external force;and a conductive material that electrically connects the charge outputelement to the terminal, wherein the sensor plate is sandwiched betweenthe first base and the charge output element, and the lid is sandwichedbetween the second base and the charge output element, a first elasticmodulus of the sensor plate is lower than a second elastic modulus ofthe side wall, and the charge output element includes crystal, and thesensor plate includes a metal material selected from stainless steel,Kovar, copper, iron, carbon steel, and titanium.
 2. The force detectoraccording to claim 1, wherein the sensor plate includes Kovar.
 3. Theforce detector according to claim 1, wherein a difference between thefirst elastic modulus and the second elastic modulus is a tenth part orless of the first elastic modulus.
 4. The force detector according toclaim 1, wherein a constituent material of the sensor plate and aconstituent material of the lid are the same.
 5. The force detectoraccording to claim 1, wherein a constituent material of the side wall isceramic.
 6. The force detector according to claim 1, wherein the chargeoutput element is a piezoelectric element.
 7. A robot comprising: anarm; an end effector provided on the arm; and a force detector providedbetween the arm and the end effector and detecting an external forceapplied to the end effector, the force detector including: a first base;a second base; and a sensor that is disposed between the first base andthe second base, the sensor being configured with: a side wall having aterminal; a sensor plate that is connected to one end of the side wall;a lid that is connected to the other end of the side wall so that aninner space is configured by the side wall, the sensor plate, and thelid; a charge output element that is disposed in the inner space andthat outputs a signal in response to the external force; and aconductive material that electrically connects the charge output elementto the terminal, wherein the sensor plate is sandwiched between thefirst base and the charge output element, and the lid is sandwichedbetween the second base and the charge output element, a first elasticmodulus of the sensor plate is lower than a second elastic modulus ofthe side wall, and the charge output element include crystal, and thesensor plate includes a metal material selected from stainless steel,Kovar, copper, iron, carbon steel, and titanium.
 8. The robot accordingto claim 7, wherein the sensor plate includes Kovar.
 9. The robotaccording to claim 7, wherein a difference between the first elasticmodulus and the second elastic modulus is a tenth part or less of thefirst elastic modulus.
 10. The robot according to claim 7, wherein aconstituent material of the sensor plate and a constituent material ofthe lid are the same.
 11. The robot according to claim 7, wherein aconstituent material of the side wall is a ceramic.
 12. The robotaccording to claim 7, wherein the charge output element is apiezoelectric element.